We as Muslims don't believe in evolution as we it's in our faith that Allah has created all living and non living things. But according to the Darwin theory, humans evolved from animals like monkeys. We also share our DNA with them. Everyone has their own belief on the existence of aliens. Some say they do, some say they don't. After the nuclear attack on Hiroshima and Nagasaki, the organisms born there weren't normal. Wether it be humans or plants. Nowadays, war is upon us. The wars in countries like Syria, Iraq etc. Maybe WW3 is not far from us. This time, countries have many weapons of mass destruction at their disposal. If these countries go at war, they will completely destroy each other and the land they live on. All those bombings and nuclear attacks will definitely change the environment of these places. So, the coming generations will live on these ruined lands and i think because of it, they would be quite different than us. Maybe they will be much more smarter than us, better than us and will try to preserve the land once used to belong to their ancestors. Maybe those people will figure out time travel and come back to us so they could blend in, learn our ways and try to use this information for their own good. So, i think that aliens won't be species coming from other planets. I think that they will be our decadents, but they won't be anything like us.
If there's any mistake in it them i would like to apologize for it. It's only a thought of mine. I hope you like it. Thank you! :)